Improvement in the production of dye-stuffs from methyl-aniline



scribed in the following arr urns HElXRHf H CARO, OF .JANNHE lM, GRAXD DUUHY OF BABES, GERMAXY.

IMPROVEMENT IN THE PRODUCTION OF DYE-STUFFS FROM METHYL-ANlLlNE.

Specification forming part of Letters Patent No. 204,796, dated June 11,1?78; application filed "March 28,1576.

To all zrhom it may concern:

Be'it known that l, HEINRICH CARD, of Mannheim, in the Grand Duchy of Baden, in the Empire of Germany, have invented a new and useful Improvement in Dye-Stuffs or Coloring-Ililatters, which improvement; is fully despecification.

The object of my invention is the production of a blue dye-stufi' or coloring-matter, which is derived from tertiary monamines, and particularly from dimethyl-aniline.

My invention is based on suggestions made by Charles Lauth, (Bericht der Deutscheu Chemischen Gesellschat't, 1876, page 1035; Bulletin de la, Socit Chimique de Paris, 1876, II Sem, page 422,) who obtained a purple coloring matter by the action of su'lphureted hydrogen and of oxidizing bodies upon the paradiamido 'tmmpouuds-of henzole, or its homologues. This reaction, however, has not yet; received any practical or industrial application, chiefly because the purple coloring-matters thus obtained offer neither in point of quality nor of economy any advantage when compared with the already existing coloring-matters of a similar tint.

By usingainong others, the chemical agents indicated by Lentil, ducing from dimethyloniline, and some other tertiary mouamines, in a direct and economical manner, a blue dye-stuff or coloriug'matter, which forms the subject of my present invention.

The proccssof producing this hlue d yestufi" or coloringnnatter is divided into three sue cessive steps: first, production of nitrosodimethylaniline; second, reduction of this substance into amidodimethylauiline; third, transformation of the latter into the blue dye stuff or coloring-mutter which I have termed Methylene-Blue.

First step; For the purpose of producing Illtl'USOUllilfillllffl51HillllG, l prepare a cold solution of ten kilograms dimethylmiiline in thirty kilograms concentrated inuriatic acid and two hundred liters water. To this mixture I add a solution. of 5.7 kilograms pure nitrite of soda (one atom) by allowing it to run in slowly while constantly agitating the mixture, for from four to fivchours. The mix: ture assumes a cllow color, and it contains I have succeeded in pro I crystals and a solution of the muriate of hi troso-dimethyl'auiline. Instead of using the pure nitrite of soda, an equivalent quantity of free nitrous acid or other compounds of this acid may he used.

Second step: For the purpose oi reducing the nitroso dimcthylauiline into amido-dimethylaniline, the ordinary agents may be used, such as metals-rim, iron, tin, or zinc; but I prefer to use for this purpose snlphureted hydrogen in the following manner: I place the ical agitating device, and with an escape for i to said, solution five hundred liters of water ao'idw 'lhep I injeeta hydrogen until the yellow color of the solution i disappears entirely. Duringthe reduction the finally it; becomes colorless, while its surface Iis covered witha blue froth or scum. In this }stage the solution contains muriate of amide dimethylaniline, and already a portion of the new sulphu-retcd coloring-matter in the forin of a colorless compound. Instead of gaseous sulphurctcd hydrogen, I can use in thesame manner sulphuret of sodium, sulphuret; of'ammonium, or other sulphurets which are do;

cessively to the solution.

Third step: The formation of the blue coloringonatter requires the addition of an exidizing, agent to the solution, which is obtained under the second stew and which is colorless. and saturated with dphuretcd hydrogen. For this purpose I and to the same slowly two hundred liters of a solution of perehloride of iron, (specific gravity 1.07,) or a sufiicient quantity ot' the same until the odor of sulphureted hydrogen disappears, the oxidizing agent is present. Instead of poi-chloride of iron, I can use an equivalent quantity of hichromate of potash, or ofa similar oxidizing agent; but I prefer the perchloride of iron on account of its cheapness. In stead of causing the oz-tidizint, agent to acton the solution of umidodimcth 'laniline contain.-

ing sulphnrctcd hydrogen, can reverse the solution of nun-into of nitroso-dimethylaniline, obtained as above stated, into a wooden tank, which is closed, and provided wit-lra mechmv the surplus sulphureted hydrogen, and I add i and fifty kilograms of concentrated m'nriatic stream of snlphuretezl- Iliquid assumes for a time a red color, and i composed by muriatic acid, to he added sac and a small surplus of 2 Y snares oper z'itioii by treating the amido-diniethylaniline first with the oxidizing agent, and then converting the colorless and inconstant oxidpredominates. For this reason the lastna-med process is more diflicult thah that first described. 4

The separation of my blue coloring-matter is efiected as follows: The mixture is saturated with common salt, and a sufticient quantity of an aqueous solution of chloride oi'zinc is added until the coloring-matter appears. com pletely precipitated. Then the mass is filtered, and from the substance remaining on the filter the blue coloring-matter, which is easily soluble in water, is separated by successive treatment with water. ,The filtered solutions of the same are again saturated with common salt, and by the addition of chloride of zinc, and by filtering, pressing, and drying, the desired coloring-matter is obtained as a compound with chloride of zinc in the fOlll'tOf a brown bronzepowder. In this form the new coloring-matter is easily soluble in water and adapted for tech nical use. For this reason the chloride of zinc is used in preference to other metallic salts andjp'recipitating agents, which also allow of bringing the new coloringanattcr in a marketable condition; but I do not coniincinyself v to the use of chloride of zinc.

The production of aniido-diinethylaniline can also, as is well knowmbe effected by the reduction of mono-nitro-diinethylaniline; and, furthermore, this base is also formed when any diazo compound is transformed into an axe compound of dimcthyl-anilinc, by bringing it together in its atomic proportion with dinicth ylaniline, and such are compound treated with reducing agents. t

For the practical manufacture of my blue eoloring-ina-tter,however, I consider the transition through the nitrosodiniethylanilinc, as

above described, the most advantageous.-

By the process above described blue coloringmJa-ttercan also be produced outofdimethylaniline, dimethyl-orthotoluidine, methyl and ethyl diphenylamine, and analogous tertiary mon amines, the same as out of dimethyl-aniline.

Such coloring-matters, however, possess .no superiority over the coloring-matter produced from dimethyl-aniline, either-as regards the cost of their production or their coloring properties. The proportions which I have given for mix ing the different substances together give a satisfactory result; but they can be changed within wide limits, and I do not limit myself, therefore, to the exact proportions above stated. I

Mynewdye-stuft'orcoloring-matter,methylene-blue, when produced in the form of a powder, has a dark-bluish color, not dichroic; it is easily soluble in water; it is but very slightly aifected by acids or alkalies; by re dncing agents, such as. zincdust, it is decolorized, and when brought in contact with air it n'illreassume its color; when it is brought together with metallic tannates, insoluble blue compounds are formed, and in dyeing and printing, this property is employed by forming said insolublecompounds in the fiber of the fabric.

In these points my methylene blue difl'ers essentially from the socalledFructhyl-blne, and from all anilineblues known to me, since these coloring-matters are reduced by alkalics, and they do not form insoluble blue compounds when brought together with metallic taunatcs, which facts are well known to practical dyer-s, and to dealers in coloring-matters and dye-stuflls.

"What I claim as new, and desire to secure by Letters Patent, is-

As a new manutlwture, a dye-stuff or coloring-matter having the characteristics above described, and produced by means substantially such as herein scti'orth, or by any other means which will produce alike result.

ln testimony that lclailn the foregoing I have hereunto set my hand and seal this 22d day of l ebruary, 1875.

. v Illil'N'ltltJ-Il' UARO. [L..s.] 

